Intercommunicating system



y Feb. 6, 1940. Lgw. KoLozsY INTERCOMMUNICATING SYSTEM 2 Sheds-Sheet 1 Filed Oct. 2l. 1956 L u? .7' INVENTOR ATTORNEY Patented Feb, 1 Y

STATES rfc INTERCOMIWUNICTNG SYSTEM .Louis W. Kolozsy, Astoria, N. Y., asslgnor, by l mesne ents, to G. S. I. Development Corporation, New New York York, N. Y., a corration or Application october 21, 193s, sensi no. losses 13 Claims.

tion. As a result of this it is possible to provide confined to the central station. Such a systeml Yso satisfactory communication from outlying .points to a central station in lsituations where it would be impossible or impractical to locate the usual signal energy generating devices at-the outlying points. The upkeep and surveillance of the signal lenergy generating equipment is therefore can be used for example to provide intercomvmunication between the bridge of a vessel and a plurality of outlying points on the vessel, e. g., engine room, life-boat stations, wheel-house, etc., even though the usual shlps generator should fail. Furthermore the communication can be achieved in any emergency 'over the existing metallic media of the ship, thus obviatlng the running of special signal conductors to all the important points of the vessel.

Another object of the invention is to provide a system of selective signalling between a. plurality of outl stations and a central station, by employing dierent signal frequencies but without requiring the relatively complicated wiring connections and apparatus usually employed for this purpose.

A feature of the invention "relates to a central.

station intercommunicating system wherein a sustained alternating current of a given frequency or frequencies, is transmitted from the central station to one or more outlying stations where it is translated into an alternating current of a different frequency to serve as a carrier ci signals back from the outlg stations to the central station. l

Another feature relates to a system of intercommunication between an outl station and r a central station whereby at the outlying station a signal modulated carrier frequency current may be transmitted to the central station employing no moving `generating equipment, oscillator generators or the like at the outlying station.

Another feature relates to novel circuit arrangements at a distant station for receiving signal energy of one frequency from a central station and converting lt locally at the distant station into signal energy of a dierent frequency for retransmission back to the central station.

A further feature relates to a system of inter l communication which is well adapted to provide two-way communication between a central point and a plurality of outlying points which may or may not be mobile, e. g., between an executives oiice and various departments in a factory, oiilce building, school, hospital or the like; or in construction operations between headquarters and l@ various points of operation which are mobile or semi-permanent in character, such as elevators or supply trains, and without the necessity of running special signal conductors to the various points. It will be seen also that this system is particularly well-suited to provide communication between a director's booth and the various points en a movie location.

A still further feature relates to the novel organization, arrangement and relative connection of parts which go to make up a reliable,

simple and eflcient system of communication between a plurality oi outlying stations and a central station.

Other features and advantages not specifically enumerated will be apparent after consideration of the following detailed descriptions and the appended claims.

While the invention will be disclosed herein as applied'to one form of intercommunicating-system it will be understood that this is done merely for purposes of explaining the inventive` concept and not by way of limitation. Likewise while the various methods are shown in diagrammatic or schematic, form, only suilcient' apparatus is disclosed in detail as to enable a thorough and complete understanding oi the invention to be attained. It will be clear to those familiar with the art of intercommunlcation that various changes in the type and details of the various parts and apparatus represented schematically may be made without departing from the spirit or scope of the invention. .Accordingly in the drawings,

Fig. 1 is a schematic diagram of a typical intercommunicating system lfor purposes of explaining the invention.

Fig. 2. is a schematic wiring diagram' showing thedetalls of one of the outlying stations of Fis. 1.

Fig. 3 ls a modification of Fig. 2. Figs. e and 5 are further modifications of Fig. 6 shows the system of Fig. 2 modined for two-way communication.

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Referring to Fig. 1 the numeral I represents any. suitable central station such as a ships bridge, a directors omce or the like. The numerals 2, 3, 4 and 5 represent a plurality of distant stations or points from which communication is to be had with the central station..

The stations 2, 3 and 5 are shown connected with the central station by a two-wire line, such as a telephone line, a telegraph line or the like, while station 4 is coupled to the central station by a space inductive link such as radio antennae or the like. The invention is not necessarily limited' to the use of special signalling lines such as telegraph or telephone lines for connecting the variousstations and therefore the two conductors shown connecting the stations in Fig. l may be the existing metallic media or adjuncts of a building structure or they may represent any -known form of signalling channel either wires or wireless. For example one conductor may be the neutral wire of a three-wire electric light or power system, and the other conductor may be the grounded framework of the building in which the central station and the various outlying stations are located.

At the central station I there are located two sources 6, l each source being designed to generate an alternating electric current of a frequency different from that generated by the other. high frequency electric currents of sustained sinusoidal wave form, and preferably, although not necessarily the two sources are connected in parallel. 6 and l are applied to the transmission networks A or links leading to the various outlying stations.

At each of the outlying stations there is provided a pick-up unit 8 consisting of circuit units such as inductances, condensers, rectifiers and the like, whereby the received electric energy is translated into carrier energy of a different frequency which is impressed back upon the same link leading from the Acentral station. In circuit with each translating unit is a signalling device 9 such as a microphone, telegraph key or the like for varying the amplitude of the outgoing translated carrier. At the central station a suitable signal reproducing device 36 is located.

Referring to Fig. 2 a typical circuit arrangement is disclosed. At the main or central station i there are provided the two sources and 'l for generating sustained alternating currents of different frequencies. Any well-known form of alternating current generator may be employed for this purpose preferably capable of generating substantially sinusoidal alternating current. The generators are connected in parallel to the two conductors i3, EI which may be the conductors of a telephone pair, a radio antenna of any known type, or any two metallic adjuncts of an existing structure such as the grounded frame-work of the building in which the generators are located, and the neutral wire of a three-wire power or lighting system. If desired the conductors I0 and il may be the conductors vof a two-wire power or lighting circuit. Connected across non-equipotential points of the networky is a tuned circuit consisting of an inductance I2 and a condenser I3, the condenserinductance combination being adjusted to resonate at the frequency of one of the generators at the central station, for example the generator 6. Connected in parallel with the first tuned circuit is another similar tuned circuit consisting of the Preferably the sources 6 and 'I generate' The outputs of the two sources inductance I4 and the condenser I5 which have been adjusted to resonate at the frequency of generator 1. Coupled .to inductance I2 is an inductance i6, and coupled to inductance I4 is a` similar inductance I1. While the drawing shows the inductances'IS and I1 as separate inductances, it will be understood that a single inductance symmetrically coupled to the inductances I2 and I4 may be employed. The conductors I8, I9 leading from the terminals of the inductances I6, I1 are connected to a suitable rectifying arrangement designated generally by the numeral 2U. Preferably, although not necessarily, this rectifying arrangement consists of two full-wave rectiers connected in bridge formation as shown. Merely for purposes of explanation, the rectifying arrangement is shown as consisting of four half-wave rectiers 2|, 22, 23 and 24. These rectiflers may be of any Well-known type but preferably are of a type not requiring separate power supply. Thus crystal, contact type rectifiers, chemical or lelectro-chemical rectiers may be employed. It will be understood that the conductors I8, I9 instead of being coupled to the tuned circuits by inductive coupling, may be coupled in any other manner well-known in the art, e. g., by means 0f resistors, resistor-condenser combinations, chokes, or choke-condenser combinations, so long as energy of the two frequencies is eiiiciently applied to the rectifier arrangement.

Since the rectlers are being supplied with two alternating currents of different fundamental frequencies, each of substantially sinusoidal wave form, there will appear in the output of the rectifier combination, namely across the conductors, 25, 26, a plurality of components consisting of a direct current component, alternating components corresponding to multiples of the input frequencies, components equivalent to the sum of the input frequencies, and components equivalent to the difference of the input. frequencies. The output conductors of the rectifier arrangement are connected in circuit with the tuned circuit 21 and the aperiodic circuit 28. The former preferably comprises an inductance 29 in parallel with a condenser 30, while the latter comprises a D. C. load resistor 3l in parallel with a by-pass condenser 32. The resistor 3i is preferably of such a value that it dissipates the D. C. component of the rectifier output and applies a suicient load on the rectifier to insure proper operation thereof, while the condenser 32 is merely of suiiicient capacity to provide a low impedance path for the alternating components. The inductance 29 and condenser 30 are ad'- justed to resonate at a frequency which is equivalent to the difference in frequency between sources 6 and 1. Coupled to inductance 29 is another inductance 33 and a series condenser 34, the said inductance 33 and condenser 34 being adjusted to resonate at the same frequency as that of the elements 29, 30. The energy in the circuit 33, 34 is applied to the connecting network I0, II through some suitable modulating device such as the microphone 35.

Located at some remote point where the signals impressed upon microphone 35 are to be received, for example at the central station I, is an electrical signal reproducing device 36 which is capable of being tuned to the frequency of the circuit 21. Preferably this signal reproducing device is provided with means for demodulat- 'ing or detecting the signal modulations in the alsace? received modulated wave transmitted from the outlying station 2 over the connecting network described. i

Instead of employing two separate frequency 'generators atI the central station I connected ,quency, i. e., frequency of source 31, but also upper and lower side-band frequencies. The modulated output of source 31 is impressed upon any of the transmission networks mentioned in connection with Fig. 1, and at the outlying station 2, two out of the three frequencies are selected by means of the tuned circuits I2-I3, and I4-I5. For example the circuit I2-I3 may be tuned to the frequency of source 31, while the circuit I4--I5 may be tuned to the frequency of either the upper side-band or the lower sideband. Alternating currents of two differing frequencies are rectified in the manner already described in connection with Fig. 1, and are used as the local carrier at the outlying station for transmitting -a signal therefrom, either to the central station I or to some other point.

Instead of employing two separate sources of alternating current at the' central station, a single source may be employed, and by suitable circuits at the outlying station this frequency may be changed for transmission back to the central station. 39 may be arranged to generatean alternating current of a chosen high frequency, which is im'- pressed upon the transmitting network after being filtered in a suitable filter 40 to suppress all the harmonics inherent in the generator 33. At the outlying station the transmission network is bridged by the circuit comprising the induct-` ance I2 and condenser I3 which are adjusted to resonance with the fundamental frequency of .the source 39. Coupled to the inductance I2 is an inductance I6 which is connected to a suitable rectier 4|,which may be of the half-wave or full-wave type. The output' of rectifier 4I will contain alternating components corresponding to multiples of the frequency of source 39v and the circuit 29, 30 will be tuned to a selected one of the alternating current multiple components, for ex'- ample to a frequency which is twice or three times the frequency of source 39. This selected frequency component may then be used as described in connection with Fig.r 2 to transmit a signal back to the central station, lter 40 .pre venting the frequency component atthe source 39, corresponding to the selected multiple atA station 2, from being` impressed upon the signal responsive device 36 which would tend to roverload the latter. 1- l A It will be obvious that the invention is not limited to a single. pick-up unit at the outlying station, or to a single station. For example the with four sources 42, 43, 44 and V45 of sustained l high frequency alternating current. cach generating' a different fundamental frequency. At' sult- Thus as shown in Fig. 4, the sourcev ably spaced points throughout the transmission network I0, II are located three pick-up units 46, 41, '46 the input circuits for each of these units being diagrammatically indicated respectively by the numerals 4950, 5I--52, 53--54; while the output circuits for impressing the output energy back upon the transmission network are designated respectively by the numerals 55-56, 51-58, 59-6IL The details of the various input and output circuits mlay be the same as those shown in Fig. 2 and further description vthereof ls )not believed necessary at this point.

'I'he electric signal responsive device' 6I at the central station can then be resonated at will to the outputfrequency produced by each of the pick-up units at the outlying station or stations. As atypical example of such an arrangement, the sources 42, 43, 44 and 45 may respectively generate the frequencies, 20,000 cycles, 30,000 cycles, 40,000 cycles, and 50,000 cycles each source being provided with a suitable switching arrangement for cutting it into and out of circuit. Let it be assumed that the input circuit 49-50 of the pick-up unit 46 is responsive to 20,000 cycles and to 30,000 cycles and that the output circuit 55-56 produces a modulated signal whose carrier'frequency corresponds to the difference, or 10,000 cycles. Likewise let it be assumed that the input circuit 5I-52 of pick-up unit 41 is tuned to be responsive to 30,000-cycles and to 40,000 cycles, and its output circuit 51--58 to the difference, namely 10,000 cycles; and also that the input circuit 53-54 for unit 48 is tuned to be responsive to 40,000 cycles and to 50,000

cycles and that the output circuit of this unit is tuned to the difference, 10,000 cycles. Under these circumstances the signal responsive device 6I may be tuned to 10,000 cycles, and it will not be necessaryA to' make any adjustment ofthe tuning of Vdevice 6I. Consequently if it is desired to receive from unit 46,. it is only necessary are switched into circuit; while for reception from unit 46, sources 44 and 45 are used. If all the sources 42 to 45 are employed then signals from all the distant units mayl be received simultaneously. l

While lthe foregoing embodiments disclose a system of communication back from the outlying stations to the central station they are capable of being used for two-way communication. Such an arrangement is illustrated in Fig. 6. In this embodiment the two high frequency sources of different frequency 6 and 1 are connected to the transmission network through a suitable modulating device shown such as the microphone 62. It will be understood, of course. that 'this method of effecting the modulation is purely schematic and that any other well-known remote pick-up unit the numeral' 63 represents -the input resonant circuit such as the circuits corresponding parts of Fig. 2 and perform similar functions. The main difference is that in Fig. 6 1

there is inserted in circuit with the load resistor 3l a telephone receiver 64. It will be understood by those familiar with the art that any modulation produced by variation of the resistance of microphone 62 in accordance with sound 'waves impressed thereon will produce in the out- -put of the rectifier inunit 63, an additional commodulating `method may be employed. At 4the (fo .l

)onent equivalent to the modulating variations, which will be reproduced in the telephone receiver 64. It will further be understood that in this case the condenser 32 will have such a value as not to bypass the low frequency speech currents but will serve merely to pass the high frequency components used for the return carrier. It is obvious that this addition will in no way effect the operation of the system whentalkingin the reverse direction.

It will also be clear to those familiar with the art while the systems disclosed can be'used for speech transmission, that any other type of signal device may be substituted for the microphone 35 to vary the resistance of the output circuit of the pick-up units for other types of transmission. For example a. telegraph key, code signalling devices, facsimile, television and other signal devices may be employed. In like manner other types of signal devices may be substituted for microphone 62 and receiver 64. Further while in some of the embodiments the several sources of high frequency currents have been shown connected in parallel, it is possible to use a series connection. Likewise instead of coupling these sources directly to the transmission network, they may be coupled thereto capacitively, inductively, or. through a suitable corrective network; filter, bridge circuitor the like, as will be obvious to those familiar with the art. Other changes may be made in the various embodiments without departing from the spirit and scope of the invention.

What I claim is:

l. The method of voice frequency signaling from a distant station to a central station which comprises transmitting a sustained alternating current of a given frequency from the central station to the distant station, converting the received alternating current at the distant station into an alternating current of a different frequency, at the distant station'modulating only the converted current in accordance with voice frequency signals, and transmitting the modulated current back to the central station.

2. The method of voice frequency signaling from a distant station to a central station which comprises generating alternating current energy only at the central station, transmitting the alternating current over a transmission network tosaid distant station, changing the frequency of said current locally at the distant station, at the distant station modulating only the changed current in accordance with voice frequency signals, and impressing the modulated current on said network for transmission to said central station.

3. The method of voice frequency signalling from a distant station to a central station which comprises generating a current having regularly recurrent amplitude variations only at the centrai station, transmitting said current over a transmission network to the distant station, dividing the received current into a plurality of frequency components, at said distant station selecting and modulating only one of said components by voice frequency signals, and impressing the modulated component on said network for transmission back to said central station.

4. The method of voice frequency signalling from a distant station to a central station which comprises generating an alternating current at the central station, transmitting said current over a transmission network to saiddistant' station, rectifying the received current to produce directly therefrom a sustained alternating current of a different frequency, at the distant station modulating only said sustained current at voice frequencies, and impressing the modulated current on said network.

5. The method of voice frequency signalling which comprises generating at one station a pair of alternating currents of different frequencies, transmitting said currents over a transmission network to another station, applying said cur- -rents at the other station to separate tuned circuits, rectifying the current from said tuned circuits to produce another alternating current of a third frequency, at said other station modulating only said other alternating current, and impressing said modulated current on said network.

6. The method of voice frequency signalling between two stations which comprises generating at the rst station a, pair of alternating currents of different frequencies, transmitting said currents over a transmission network to the second station, passing the currents through separate tuned circuits at the second station, rectifying the current from said tuned circuits to produce a third alternating current of a frequency diiferent from the said pair of currents, at said second ystation modulating only said third current in accordance with signals, and impressing said modulated current on said network.

7. The method of voice frequency signalling between two stations which comprises generating at the rst station a pair of alternating currents of different frequencies, transmitting said currents simultaneously over a transmission network, passing said currents at the second-station through respective tuned circuits, combining and rectifying the tuned circuit currents, suppressing the direct current component of the rectified current, selecting a frequency component of the rectier output having a frequency different from the first-mentioned frequencies, at said second station modulating only said selected component, and impressing said modulated component on said network.

8 The method of voice frequency signalling which comprises generating at a first station an alternating current, modulating at said station said alternating current by a second alternating current of lower frequency, transmitting the fundamental and at least one side-band of the modulated alternating current to a second station, passing the fundamental and at least one sideband through respective tuned circuits at the second station, combining and rectifying the output of the tuned circuits to produce a third a1- ternating current having a frequency equal to the difference between said fundamental and said side-band, and at said second station modu- `lating only said third alternating current in accordance with signals.

9. The method ofI voice frequency signalling which comprises generating at a first station an alternating current, suppressing substantially all but the fundamental frequency of said current, transmitting said fundamental to a second station, passing said fundamental through a rectifier at the second station, selecting from the output of said rectier a component having a frequency different from said fundamental, at said second station modulating only said selected component in accordance with voice frequency signais, and transmitting the modulated component from the second'station to the first station.

10. In a telephone system of the character described the combination of a transmission network including a. receiving station adapted to receive an unmodulated alternating current from a distant station, a tuned circuit coupled to said network, meanscoupled to said network. to convert the received current into another alternating current of a different frequency, means at .said receiving station to modulate only said other current at voice frequency, and means to lmpress the modulated current on said network.

. 11. In a telephone system of the character described the combination of a transmission network adapted to receive from a distant station a pair of alternating currents each of a diierent frequency from the other, a pair of tuned circuits coupled to said network each circuit being tuned to one of said currents, a frequency converter, means to couple said tuned circuits to said converter to produce in the output of said converter an alternating current of a third frequency, means at said receiving station -to modulate only said third current in accordance with voice frequency, and means to impress the modulated current on said network for transmission to a distant station.

`and means to impress i2. In a telephone system of the character described the combination of, a first station, means at said station for generating a pair oi alternating currents of different `frequencies, a second station, a transmission network linking the two stations, means to impress both said currents simultaneously on said network, a pair of tuned circuits at the second station each tuned to one of said currents, a rectifying device, means to couple said tuned circuits to said device to produce in the output of said device a current of a third frequency, means to modulatesaid third current in accordance with telep'hone signals, saidfmodulated current on said network.

13. A system according to claim 12 in which one of the alternating currents at therst station is modulated uponv the other alternating current and the transmission from 'the first station to the second station is effected with at least one of the side-bands of the modulated current.

" lnorms w. xowzsY'. 

